An image reading unit, such as an image scanner, copying machine, or the like, one having the function of reading images on two types of originals, i.e., a reflection original such as a magazine and a transparent original such as a photographic film, is known.
The image reading unit includes a unit main body incorporating an image reader having a built-in image sensor or the like, and a platen unit pivotally provided to the unit main body and located on the unit main body. A transparent original light source is incorporated in the platen unit.
When an image on a transparent original such as a film is to be read, the transparent original is placed on an original table glass formed on the upper surface of the unit main body. The transparent original light source incorporated in the unit main body is turned on and light transmitted through the transparent original is detected by the image reader. Thus, the transparent original image is read.
Conventionally, when a transparent original is to be read, the transparent original is put in a holding tool called a film holder, and the film holder is set on the original table glass. Usually, the illumination range of the transparent original light source is smaller than the size of the original table glass, and accordingly the transparent original must be set in a transparent original reading area on the original table glass. Conventionally, in some image reading apparatus, in order to facilitate the setting operation, the film holder is set by abutting it against one corner of the original table glass by using the corner of the rectangular film holder as a positioning portion. Thus, a transparent original in the film holder is set in the transparent original reading area (for example, see Japanese Patent Laid-Open Nos. 2000-358132 and 2003-5304).
The above conventional examples have the following problems.
Conventionally, in the image reading apparatus that can read images on two types of originals, i.e., a reflection original and transparent original, the transparent original is mounted in the film holder, and the film holder is placed on the original table glass, as described above. The film holder is a member separate from the reading unit and used only when a transparent original is to be read. Hence, the film holder is kept at a place different from the image reading apparatus, and taken out and used when necessary.
Generally, an image reading apparatus of this type is often used to read an image on a reflection original rather than a transparent original, and a film holder is not used frequently. For this reason, once the user wishes to read a film image, the film holder may sometimes be missed, and the film image cannot be read. Also, it is cumbersome to prepare the film holder.
In the image reading apparatus of this type, usually, a transparent original readable area where the image can be read by illuminating the transparent original is smaller than a reflection original readable area. Accordingly, to read the film image correctly, the film holder must be placed at a position where the mounted film comes in the transparent original readable area. Considering the process after the reading, it is important to set the film holder such that the mounted film may not be read with a skew.
According to the method disclosed in Japanese Patent Laid-Open Nos. 2000-358132 and 2003-5304, the film holder is positioned by abutting its corner against one corner of the original table glass. As the film holder is placed by merely abutting its corner against the corner of the original table glass, if the user accidentally touches the film holder with his or her hand or when the user closes the platen unit, the position of the film holder may be shifted. Consequently, the film is set such that it is partly outside the transparent original reading area, or may be set with a skew. Accordingly, part of the film image cannot be read, or a skew image is read.
Conventionally, when an image is to be read while the film is set in a film holder, the film holder must be set such that the upper surface (base surface) of the film opposes the reading unit main body and that the lower surface (emulsion surface or film surface) of the film opposes the transparent original light source. When the film is mounted in the film holder and the film holder is set on the original table, whether the upper surface of the film faces up or the lower surface of the film faces up cannot be distinguished easily, and a setting error is hardly noticeable. Sometimes the film is erroneously set such that its upper surface opposes the transparent original light source, and the image is read while the user does not notice that the upper and lower surfaces of the film are reversed. Then, an image is read with the upper and lower surfaces reversed.